Oil on the Sea Floor 



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Recent observations concerning the 

 fate of oil in the ocean after spills and 

 leaks such as those in the Santa Bar- 

 bara channel and from the S.S. Torrey 

 Canyon off the English coast have led 

 some investigators to conclude that 

 dispersal methods that involve re- 

 moving the oil from the surface by 

 overpowering its natural buoyancy 

 (thus transferring it to the sea bot- 

 tom) are potentially more harmful to 

 the environment than methods that 

 leave the oil dispersed but floating on 

 the ocean surface. 



Since sinking methods involve the 

 use of extremely cheap agents (sand, 

 ashes, and the like) and since they 

 generally remove the oil before it can 

 contact beaches, yacht hulls, and 

 other recreational surfaces, there are 

 strong economic and aesthetic argu- 

 ments in favor of their continued use. 



On the other hand, if it could be 

 shown that the transferral of toxic 

 petroleum constituents to the sea floor 

 would result in damage to demersal 

 fisheries, there are strong arguments 

 for establishing an effective interna- 

 tional regime to control both drilling 

 for and seaborne transportation of 

 petroleum, wherever the possibility 

 exists that it may be deposited in 

 quantity upon the sea surface, and to 

 fix responsibility, assess damages, and 

 compensate those economically in- 

 jured in case such an event occurs. 



Status of Scientific Knowledge 



Current scientific knowledge rele- 

 vant to the problem of petroleum on 

 the sea surface and sea floor is far 

 from adequate with respect to reliable 

 predictions of the possible harmful 

 effects of removing petroleum or 

 petroleum residues from the sea sur- 

 face by sinking them to the sea floor. 



Amounts of Hydrocarbons in 

 Marine Sediments — We do know 

 already, from extensive investigations 



of the chemical composition of ocean 

 sediments in many parts of the world, 

 that detectable quantities of paraffins, 

 aromatics, and asphalts — chemically 

 indistinguishable from petroleum 

 fractions — are present in ocean sedi- 

 ments. (See Figure X-17) Ironically, 

 these investigations have been carried 

 out primarily to determine the sources 

 of oil in sediments, not the fate of oil 

 in the sea. 



Emery summarized much of this 

 work in 1960 in his book The Sea 

 Off Southern California. He found 

 the greatest rate of accumulation of 

 hydrocarbons in marine sediments to 

 be in certain stagnant basins, where 

 they could amount to as much as 

 0.15 percent of the dry weight of sedi- 

 ment. Emery's calculations showed 

 that about 880 tons of such material 

 were deposited annually in the sedi- 

 ments over an area of 78,000 square 

 kilometers, compared to an annual 

 production of 135,000 tons of similar 

 materials by the phytoplankton over 

 the same area. Disregarded entirely 



in this computation is the possibility 

 that any of the hydrocarbon mal 

 currently being deposited in the sedi- 

 ments is reworked from the numer- 

 ous seeps in this region of the Cali- 

 fornia coast. 



Recent work by Horn, Teal, and 

 Backus of Woods Hole Oceanographic 

 Institution not only shows that float- 

 ing lumps of petroleum residue are 

 common on the sea surface but sug- 

 gests two methods by which the con- 

 stituents of such lumps can be trans- 

 ferred to the sea floor through natural 

 processes as well as a natural method 

 for disposing of the material at the 

 sea surface. 



Natural Sinking Processes — 

 Goose-neck barnacles, which at cer- 

 tain seasons of the year attach them- 

 selves to any suitable firm substrate 

 near the sea surface, were found 

 adhering to floating lumps of petro- 

 leum. Since these creatures secrete a 

 calcareous exoskeleton, they are sig- 

 nificantly heavier than sea water; 



Figure X-17 — PETROLEUM HYDROCARBON CONTAMINATION 

 IN THE MARINE ENVIRONMENT 



SEDIMENTS 



Location ppm 



West Falmouth, Mass., USA ._._ - ..up to 12,400 



(dry wt.) 



West Falmouth, Mass., USA 21-3,000 



(wet wt.) 



Narragansett Bay, Rhode Island, USA - - 50-3,560 



(dry wt.) 



Chedabucto Bay, Canada _~ 0-6.8 



(dry wt.) 



The table shows some measurements of petroleum hydrocarbons found in sediments 

 of coastal waters. Studies have shown that marine organisms are adversely affected 

 by petroleum and that complex mixtures of petroleum hydrocarbons are present 

 both in sediments and marine organisms. It is estimated that the input to U.S. 

 coastal waters of petroleum hydrocarbon via sewage effluents ranges from 12,000 

 to 150,000 metric tons per year. 



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